Vibrators and widely used in seismic exploration. Typically, a vehicle such as a truck supports a large, heavy, substantially horizontal base plate that is connected by vertical columns or stilt structure to an inertia mass. The inertia mass contains a linear actuator that causes the base plate to move in reciprocating motion along a vertical or horizontal axis in reaction to the momentum of the inertia mass. The reciprocating base plate injects a vibratory wave train into the earth that may last more than 20 seconds. The frequency of the vibratory wave may vary continuously from 5 to more than 80 Hertz creating a sweep signal. During the sweep cycle a portion of the vehicle's weight is applied to the base plate through compliant isolation members such as airbags or springs. The weight of the vehicle increases the coupling of the base plate with the earth while the isolation members reduce the amount of vibratory energy transferred to the vehicle.
In operation, the vibrator assembly, and the stilt structure in particular, is subject to extreme tensional and compressional forces caused by the reciprocating inertia mass. In order to combat structural fatigue in the stilt structure, all components are structurally stiff and rigidly fastened to each other either by way of bolts or welds. Despite many oversized components and rigid connections structural failures are commonplace particularly in connections between horizontal and vertical components experiencing dynamic bending moments or stress.